This invention relates to a plasma apparatus. This invention also relates to associated methods of performing a treatment step using said plasma apparatus. This invention further relates to a remote plasma source for sustaining an inductively coupled plasma.
Plasma processing techniques are commonly used in many industrial applications, such as in semiconductor processing. The plasma used in plasma processing techniques may be generated in a number of ways. One of the more common methods is using an inductively coupled plasma (ICP) source. An ICP source may be a remote plasma generation source, or the plasma may be inductively coupled within the processing chamber directly.
Typically, an inductively coupled plasma is generated by applying an RF signal to an antenna, coil or band that is positioned externally to a processing chamber. The antenna, coil or band forms a primary winding of a transformer, and is used to couple energy into the processing chamber via a dielectric container or window. If a suitable gas or gaseous mixture is introduced into the processing chamber at a suitably low pressure, a gas discharge is produced. The removal of heat from this type of system can be a problem, owing to the relatively poor thermal conductivity of convention dielectric materials. It is possible to use more advanced dielectric materials with improved thermal characteristics. An example of an advanced dielectric material is AlN. However, these advanced materials are costly and also they impose design limitations which limit their use in many applications.
European patent application published as EP3214637 discloses a chamber having walls comprising a metallic band, which acts as a single turn structure of an ICP plasma source. The metallic band is disposed between two dielectric sections. The dielectric sections have different thermal expansion coefficients to the metallic band, and can lead to problems with thermal expansion mismatch.
It is desirable to more efficiently dissipate heat from the plasma generation source and processing chamber, whilst avoiding thermal expansion mismatch. There is also a need to operate a plasma processing chamber at higher plasma densities in order to increase reaction speeds. For example, a plasma with a high density is typically used during cleaning steps to more efficiently remove residues from the processing chamber. It is also desirable to develop a processing chamber suitable for operating at higher power, with an improved coupling efficiency between the power inputted and the plasma generated.